JAVASCRIPT 在线编辑器| BEGTUT.COM

<!DOCTYPE html>
<html>
<body>

<p>如果值为 Number.NaN（非数字），Number.isNaN() 函数返回 true，否则返回 false。</p>

<p>点击按钮检查数字是否为NaN。</p>

<button onclick="myFunction()">试一试</button>

<p id="demo"></p>

<p><strong>注意</strong> Number.isNaN() 函数在 IE 11（及更早版本）中不受支持。</p>

<script>
function myFunction() {
  var res = "";
  res = res + Number.isNaN(123) + ": 123<br>";
  res = res + Number.isNaN(-1.23) + ": -1.23<br>";
  res = res + Number.isNaN(5-2) + ": 5-2<br>";
  res = res + Number.isNaN(0) + ": 0<br>";
  res = res + Number.isNaN('123') + ": '123'<br>";
  res = res + Number.isNaN('Hello') + ": 'Hello'<br>";
  res = res + Number.isNaN('2005/12/12') + ": '2005/12/12'<br>";
  res = res + Number.isNaN('') + ": ''<br>";
  res = res + Number.isNaN(true) + ": true<br>";
  res = res + Number.isNaN(undefined) + ": undefined<br>";
  res = res + Number.isNaN('NaN') + ": 'NaN'<br>";
  res = res + Number.isNaN(NaN) + ": NaN<br>";
  res = res + Number.isNaN(0 / 0) + ": 0 / 0<br>";

document.getElementById("demo").innerHTML = res;
}
</script>

</body>
</html>